Speedometer



Jan. 24, 1933. A, Els'ELE l 1,895,029

SPEBDOMETER a f r a cian. F24.,

a fmammmfm .Application illed April 1?, 1930, Serial No. M, and

magnets. The lamels are arranged above and coaxially with the rotating magnets and can be radially adjusted with respect to the axis of rotation in order to divert more or less of the magnetic lines of force of the magnets. Accordingly the magnets exert a greater or minor torque on the indicating armature.

A further feature of the invention resides in means arranged outside of the speedom eters allowing to easily adjust the shunt magnetic field even while speedometer is working.

Other features of the invention will be apparent from the following description.

In the drawing, Fig. l is a vertical sectional elevation of the new speedometer, and Fig. 2 is a plan View of the speedometer with the' dial plate removed, and Fig. 3 is a plan view of the s eedometer with the dial plate in place. `ig. 4 is a cross-section on the line 1-4 of Fig. 2.

The C-shaped magnet 2 is rotated b the driving shaft 1. Between the cylin rical poles of the magnet there is arranged the coaxial cylindrical core 2. of soft iron rotating with the magnet. By this arrangement an annular air gap is formed which is penetrated by magnetic lines of force and into which enters the shell of the indicating armature 3 preferably consisting of aluminium.

ln the armature 3 the shaft 4 of which is so journalled as to easily rotate, eddy currents are produced by the rotating magnetic field; the armature is thus subjected to the action of said iield whereby it is displaced :from its initial or zero position in which it is restrained by the force of the spring 5. The angle or" deflection is a measure of the velocity of revolution of the magnet 29 and this velocity is shown by the position or" the pointer G.

The iris diaphragm is arranged above the armature 3 as a magnetic shunt parallel to the magnetic field cutting the armature. The

iris diaphragm consists the solid mount ing 7, the adjustable 8 and the lamels Si of a good conductor o'f magnetism. The latter move radially when the ring 8 is'turned. The more the lamels 9 are turned inwards7 the morelines of force will loe diverted by them into the shunt, and the less will be the strength of the magnetic eld in the armature gap, i. e. the less willi be the strength of the torque exerted on the armature 'The 60 dotted line 10 in Fig. 2 indicates the inner, position of the lamels. The lamels are suitably insulated against each other for example by coating them with a layer of lacquer in order to diminish the formation otv eddy -currents in the diaphragm.

In Figure 4 one lamel designated by the numeral 9 has been shown in Fig. 2 prrtly in full lines and partly in dotted lines. The

lamel has on its lower surface a pivot 1" ro- 70 tatable in the mounting 7. On the upper surface it has a pin 18 engaging into a slot 19 of the rotatable ring 8. The straight line connecting the centres of the pivot and the pin forms with the slot 19 an acute angle so that 75 diameters of the wheels are hence decreased. '85

But the indication of the tachometer depends on the effective diameter of the'wheel the axle of which drives the instrument.' It is now easily possible at any time to adjust the tachometer even while it is working to bring it in accordance with the real diameter of `the wheel.

The rotatable ring 8 is provided with a seg- .ment of a toothed wheei 11 meshing with the gear 12, the axle 13 ot which protrudes to the outside of the instrument. A pointer 14 con nected with the ring 8 is led through a slot of the dial plate 15 and marlrs the position oi* the diaphragm on a special graduation made according to the diameters of the wheels.

If therefore a certain diameter of a wheel is known the knob 16 is to be turned till the pointer 14 reaches the corresponding indication.

The common method of adjusting the tachometers according to a middle diameter of the wheel may therefore be replaced by the exact gauging according to the real diameter.

What I claim is:

1. In a speedometer, a rotating magnet, an armature rotatable about the same axis as the magnet and forming the speed indicating member, a plurality of radially adjustable members of a good conductor of magnetism arranged coaxlally with and above the rotating magnet and the armature, and adapted to divert a part of the lines of force out of .the magnetic field cutting the armature, and

means accessible outside of the speedometer, for operating the said adjustable members.

2. In a speedometer, a rotating magnet, an armature rotatable about the same axis as the magnet and forming the speed indicating member, a plurality of radially adjustable 4 members of a good conductor of magnetism arranged coaxially with and above the rotating magnet and the armature and adapted to divert a art of the lines of force out of the magnetic field cutting the armature, means accessible outside of the speedometer for opera-ting the said adjustable members, and

means indicating the adjusted position of the latter members.

In testimony whereof I affix my signature.

ALBERT EISELE. 

